gdb/ui-file.h

   1 /* UI_FILE - a generic STDIO like output stream.
   2    Copyright (C) 1999-2022 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef UI_FILE_H
  20 #define UI_FILE_H
  21
  22 #include <string>
  23 #include "ui-style.h"
  24
  25 /* The abstract ui_file base class.  */
  26
  27 class ui_file
  28 {
  29 public:
  30   ui_file ();
  31   virtual ~ui_file () = 0;
  32
  33   /* Public non-virtual API.  */
  34
  35   void printf (const char *, ...) ATTRIBUTE_PRINTF (2, 3);
  36
  37   /* Print a NUL-terminated string whose delimiter is QUOTER.  Note
  38      that these routines should only be called for printing things
  39      which are independent of the language of the program being
  40      debugged.
  41
  42      This will normally escape backslashes and instances of QUOTER.
  43      If QUOTER is 0, it won't escape backslashes or any quoting
  44      character.  As a side effect, if you pass the backslash character
  45      as the QUOTER, this will escape backslashes as usual, but not any
  46      other quoting character.  */
  47   void putstr (const char *str, int quoter);
  48
  49   /* Like putstr, but only print the first N characters of STR.  If
  50      ASYNC_SAFE is true, then the output is done via the
  51      write_async_safe method.  */
  52   void putstrn (const char *str, int n, int quoter, bool async_safe = false);
  53
  54   int putc (int c);
  55
  56   void vprintf (const char *, va_list) ATTRIBUTE_PRINTF (2, 0);
  57
  58   /* Methods below are both public, and overridable by ui_file
  59      subclasses.  */
  60
  61   virtual void write (const char *buf, long length_buf) = 0;
  62
  63   /* This version of "write" is safe for use in signal handlers.  It's
  64      not guaranteed that all existing output will have been flushed
  65      first.  Implementations are also free to ignore some or all of
  66      the request.  puts_async is not provided as the async versions
  67      are rarely used, no point in having both for a rarely used
  68      interface.  */
  69   virtual void write_async_safe (const char *buf, long length_buf)
  70   { gdb_assert_not_reached ("write_async_safe"); }
  71
  72   /* Some ui_files override this to provide a efficient implementation
  73      that avoids a strlen.  */
  74   virtual void puts (const char *str)
  75   { this->write (str, strlen (str)); }
  76
  77   virtual long read (char *buf, long length_buf)
  78   { gdb_assert_not_reached ("can't read from this file type"); }
  79
  80   virtual bool isatty ()
  81   { return false; }
  82
  83   /* true indicates terminal output behaviour such as cli_styling.
  84      This default implementation indicates to do terminal output
  85      behaviour if the UI_FILE is a tty.  A derived class can override
  86      TERM_OUT to have cli_styling behaviour without being a tty.  */
  87   virtual bool term_out ()
  88   { return isatty (); }
  89
  90   /* true if ANSI escapes can be used on STREAM.  */
  91   virtual bool can_emit_style_escape ()
  92   { return false; }
  93
  94   virtual void flush ()
  95   {}
  96
  97   /* If this object has an underlying file descriptor, then return it.
  98      Otherwise, return -1.  */
  99   virtual int fd () const
 100   { return -1; }
 101
 102   /* Return true if this object supports paging, false otherwise.  */
 103   virtual bool can_page () const
 104   {
 105     /* Almost no file supports paging, which is why this is the
 106        default.  */
 107     return false;
 108   }
 109
 110 private:
 111
 112   /* Helper function for putstr and putstrn.  Print the character C on
 113      this stream as part of the contents of a literal string whose
 114      delimiter is QUOTER.  */
 115   void printchar (int c, int quoter, bool async_safe);
 116 };
 117
 118 typedef std::unique_ptr<ui_file> ui_file_up;
 119
 120 /* A ui_file that writes to nowhere.  */
 121
 122 class null_file : public ui_file
 123 {
 124 public:
 125   void write (const char *buf, long length_buf) override;
 126   void write_async_safe (const char *buf, long sizeof_buf) override;
 127   void puts (const char *str) override;
 128 };
 129
 130 /* A preallocated null_file stream.  */
 131 extern null_file null_stream;
 132
 133 extern int gdb_console_fputs (const char *, FILE *);
 134
 135 /* A std::string-based ui_file.  Can be used as a scratch buffer for
 136    collecting output.  */
 137
 138 class string_file : public ui_file
 139 {
 140 public:
 141   /* Construct a string_file to collect 'raw' output, i.e. without
 142      'terminal' behaviour such as cli_styling.  */
 143   string_file () : m_term_out (false) {};
 144   /* If TERM_OUT, construct a string_file with terminal output behaviour
 145      such as cli_styling)
 146      else collect 'raw' output like the previous constructor.  */
 147   explicit string_file (bool term_out) : m_term_out (term_out) {};
 148   ~string_file () override;
 149
 150   /* Override ui_file methods.  */
 151
 152   void write (const char *buf, long length_buf) override;
 153
 154   long read (char *buf, long length_buf) override
 155   { gdb_assert_not_reached ("a string_file is not readable"); }
 156
 157   bool term_out () override;
 158   bool can_emit_style_escape () override;
 159
 160   /* string_file-specific public API.  */
 161
 162   /* Accesses the std::string containing the entire output collected
 163      so far.
 164
 165      Returns a non-const reference so that it's easy to move the
 166      string contents out of the string_file.  E.g.:
 167
 168       string_file buf;
 169       buf.printf (....);
 170       buf.printf (....);
 171       return std::move (buf.string ());
 172   */
 173   std::string &string () { return m_string; }
 174
 175   /* Provide a few convenience methods with the same API as the
 176      underlying std::string.  */
 177   const char *data () const { return m_string.data (); }
 178   const char *c_str () const { return m_string.c_str (); }
 179   size_t size () const { return m_string.size (); }
 180   bool empty () const { return m_string.empty (); }
 181   void clear () { return m_string.clear (); }
 182
 183 private:
 184   /* The internal buffer.  */
 185   std::string m_string;
 186
 187   bool m_term_out;
 188 };
 189
 190 /* A ui_file implementation that maps directly onto <stdio.h>'s FILE.
 191    A stdio_file can either own its underlying file, or not.  If it
 192    owns the file, then destroying the stdio_file closes the underlying
 193    file, otherwise it is left open.  */
 194
 195 class stdio_file : public ui_file
 196 {
 197 public:
 198   /* Create a ui_file from a previously opened FILE.  CLOSE_P
 199      indicates whether the underlying file should be closed when the
 200      stdio_file is destroyed.  */
 201   explicit stdio_file (FILE *file, bool close_p = false);
 202
 203   /* Create an stdio_file that is not managing any file yet.  Call
 204      open to actually open something.  */
 205   stdio_file ();
 206
 207   ~stdio_file () override;
 208
 209   /* Open NAME in mode MODE, and own the resulting file.  Returns true
 210      on success, false otherwise.  If the stdio_file previously owned
 211      a file, it is closed.  */
 212   bool open (const char *name, const char *mode);
 213
 214   void flush () override;
 215
 216   void write (const char *buf, long length_buf) override;
 217
 218   void write_async_safe (const char *buf, long length_buf) override;
 219
 220   void puts (const char *) override;
 221
 222   long read (char *buf, long length_buf) override;
 223
 224   bool isatty () override;
 225
 226   bool can_emit_style_escape () override;
 227
 228   /* Return the underlying file descriptor.  */
 229   int fd () const override
 230   { return m_fd; }
 231
 232   virtual bool can_page () const override
 233   {
 234     return m_file == stdout;
 235   }
 236
 237 private:
 238   /* Sets the internal stream to FILE, and saves the FILE's file
 239      descriptor in M_FD.  */
 240   void set_stream (FILE *file);
 241
 242   /* The file.  */
 243   FILE *m_file;
 244
 245   /* The associated file descriptor is extracted ahead of time for
 246      stdio_file::write_async_safe's benefit, in case fileno isn't
 247      async-safe.  */
 248   int m_fd;
 249
 250   /* If true, M_FILE is closed on destruction.  */
 251   bool m_close_p;
 252 };
 253
 254 typedef std::unique_ptr<stdio_file> stdio_file_up;
 255
 256 /* Like stdio_file, but specifically for stderr.
 257
 258    This exists because there is no real line-buffering on Windows, see
 259    <http://msdn.microsoft.com/en-us/library/86cebhfs%28v=vs.71%29.aspx>
 260    so the stdout is either fully-buffered or non-buffered.  We can't
 261    make stdout non-buffered, because of two concerns:
 262
 263     1. Non-buffering hurts performance.
 264     2. Non-buffering may change GDB's behavior when it is interacting
 265        with a front-end, such as Emacs.
 266
 267    We leave stdout as fully buffered, but flush it first when
 268    something is written to stderr.
 269
 270    Note that the 'write_async_safe' method is not overridden, because
 271    there's no way to flush a stream in an async-safe manner.
 272    Fortunately, it doesn't really matter, because:
 273
 274     1. That method is only used for printing internal debug output
 275        from signal handlers.
 276
 277     2. Windows hosts don't have a concept of async-safeness.  Signal
 278        handlers run in a separate thread, so they can call the regular
 279        non-async-safe output routines freely.
 280 */
 281 class stderr_file : public stdio_file
 282 {
 283 public:
 284   explicit stderr_file (FILE *stream);
 285
 286   /* Override the output routines to flush gdb_stdout before deferring
 287      to stdio_file for the actual outputting.  */
 288   void write (const char *buf, long length_buf) override;
 289   void puts (const char *linebuffer) override;
 290 };
 291
 292 /* A ui_file implementation that maps onto two ui-file objects.  */
 293
 294 class tee_file : public ui_file
 295 {
 296 public:
 297   /* Create a file which writes to both ONE and TWO.  ONE will remain
 298      open when this object is destroyed; but TWO will be closed.  */
 299   tee_file (ui_file *one, ui_file_up &&two);
 300   ~tee_file () override;
 301
 302   void write (const char *buf, long length_buf) override;
 303   void write_async_safe (const char *buf, long length_buf) override;
 304   void puts (const char *) override;
 305
 306   bool isatty () override;
 307   bool term_out () override;
 308   bool can_emit_style_escape () override;
 309   void flush () override;
 310
 311   virtual bool can_page () const override
 312   {
 313     /* If one of the underlying files can page, then we allow it
 314        here.  */
 315     return m_one->can_page () || m_two->can_page ();
 316   }
 317
 318 private:
 319   /* The two underlying ui_files.  */
 320   ui_file *m_one;
 321   ui_file_up m_two;
 322 };
 323
 324 /* A ui_file implementation that filters out terminal escape
 325    sequences.  */
 326
 327 class no_terminal_escape_file : public stdio_file
 328 {
 329 public:
 330   no_terminal_escape_file ()
 331   {
 332   }
 333
 334   /* Like the stdio_file methods, but these filter out terminal escape
 335      sequences.  */
 336   void write (const char *buf, long length_buf) override;
 337   void puts (const char *linebuffer) override;
 338 };
 339
 340 #endif